U.S. patent application number 13/869390 was filed with the patent office on 2013-09-12 for electro-conductive member, process cartridge, and electrophotographic apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Satoshi Koide, Hidekazu Matsuda, Noboru Miyagawa.
Application Number | 20130236214 13/869390 |
Document ID | / |
Family ID | 48573845 |
Filed Date | 2013-09-12 |
United States Patent
Application |
20130236214 |
Kind Code |
A1 |
Koide; Satoshi ; et
al. |
September 12, 2013 |
ELECTRO-CONDUCTIVE MEMBER, PROCESS CARTRIDGE, AND
ELECTROPHOTOGRAPHIC APPARATUS
Abstract
Provided is an electro-conductive member in which a C set hardly
occurs. The electro-conductive member is an electro-conductive
member including an electro-conductive substrate and a porous
rubber elastic layer, in which the porous rubber elastic layer
includes closed cells including particles, and the particles are
not fixed to inner walls of the closed cells.
Inventors: |
Koide; Satoshi; (Otsu-shi,
JP) ; Matsuda; Hidekazu; (Susono-shi, JP) ;
Miyagawa; Noboru; (Suntou-gun, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
48573845 |
Appl. No.: |
13/869390 |
Filed: |
April 24, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2012/007702 |
Nov 30, 2012 |
|
|
|
13869390 |
|
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Current U.S.
Class: |
399/176 |
Current CPC
Class: |
G03G 15/0818 20130101;
G03G 15/0233 20130101; G03G 15/1685 20130101 |
Class at
Publication: |
399/176 |
International
Class: |
G03G 15/02 20060101
G03G015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2011 |
JP |
2011-267222 |
Claims
1. An electro-conductive member, comprising: an electro-conductive
substrate; and a porous rubber elastic layer, wherein: the porous
rubber elastic layer includes a closed cell including a particle;
and the particle is not fixed to an inner wall of the closed
cell.
2. The electro-conductive member according to claim 1, wherein a
volume average particle diameter D1 of the particle and a volume
average diameter D2 of the closed cell satisfy a relationship of
0.1(D1/D2) 0.8.
3. The electro-conductive member according to claim 2, wherein the
D2 is 20 .mu.m or more and 200 .mu.m or less.
4. The electro-conductive member according to claim 1, wherein the
particle includes an acrylic resin or a silicone resin.
5. The electro-conductive member according to claim 1, wherein the
electro-conductive member has a roller shape.
6. A process cartridge, comprising: the electro-conductive member
according to claim 1; and a body to be charged, which is integrated
with the electro-conductive member, the process cartridge being
attachable to and detachable from a main body of an
electrophotographic apparatus.
7. An electrophotographic apparatus, comprising: the
electro-conductive member according to claim 1; and a body to be
charged.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/JP2012/007702, filed Nov. 30, 2012, which
claims the benefit of Japanese Patent Application No. 2011-267222,
filed Dec. 6, 2011.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an electro-conductive
member, and a process cartridge and an electrophotographic
image-forming apparatus (hereinafter referred to as
"electrophotographic apparatus") which use the electro-conductive
member.
[0004] 2. Description of the Related Art
[0005] A roller-shaped electro-conductive member (hereinafter
sometimes referred to as "conductive roller") to be used in a
charging roller or the like in an electrophotographic apparatus is
provided with a flexible layer so that an appropriate nip width is
obtained between the electro-conductive member and an abutment
member such as an electrophotographic photosensitive member. An
example of such flexible layer is a porous rubber layer containing
cells. In this case, the cells in the rubber layer are formed by,
for example, addition of a foaming agent or hollow particles.
[0006] Meanwhile, in the case where a conductive roller provided
with such rubber layer is left to stand still in abutment with an
abutment member over a long period of time, strain which is not
recovered easily, that is, a permanent compression set or a
compression set (hereinafter sometimes referred to as "C set") may
occur in the abutment portion. In particular, in a high-temperature
and high-humidity environment, an amount of the C set is liable to
increase.
[0007] In the case where the electrophotographic photosensitive
member is charged by using, as the charging roller, a charging
roller in which the C set has occurred, discharge generated in a
gap between a surface of the conductive roller and a surface of the
electrophotographic photosensitive member becomes unstable when a
portion in which the C set had occurred (hereinafter referred to as
"C set portion") passes a discharge region. That is, a difference
in charging ability occurs between the C set portion of the
electro-conductive member and a portion in which the C set has not
occurred. As a result, an electrophotographic image having
streak-like unevenness in image density (hereinafter referred to as
"C set image") may be formed in a site corresponding to the C set
portion of the electro-conductive member.
[0008] As a charging member capable of alleviating the C set
causing the above-mentioned phenomenon, Japanese Patent Application
Laid-Open No. 2006-154441 discloses a charging member which is
formed of a conductive foam and has average cell diameters varying
depending upon the sites.
SUMMARY OF THE INVENTION
[0009] The inventors of the present invention studied the charging
member according to Japanese Patent Application Laid-Open No.
2006-154441 and confirmed a certain effect of suppressing the C
set. However, in recent years, the inventors of the present
invention recognized that it is necessary to develop a charging
member in which the C set hardly occurs additionally, in order to
satisfy the requirements of higher process speed, higher image
quality, and higher durability in an electrophotographic
apparatus.
[0010] The present invention is directed to providing an
electro-conductive member in which the C set hardly occurs. The
present invention is also directed to providing a process cartridge
and an electrophotographic apparatus capable of forming a
high-quality electrophotographic image stably.
[0011] According to one aspect of the present invention, there is
provided an electro-conductive member, including an
electro-conductive substrate; and an elastic layer, in which: the
elastic layer includes a closed cell including a particle; and the
particle is not fixed to an inner wall of the closed cell.
[0012] According to another aspect of the present invention, there
is also provided a process cartridge, including the above-mentioned
electro-conductive member; and a body to be charged, which is
integrated with the electro-conductive member, the process
cartridge being attachable to and detachable from a main body of an
electrophotographic apparatus. According to the present invention,
there is also provided an electrophotographic apparatus, including
the above-mentioned electro-conductive member; and a body to be
charged.
[0013] According to the present invention, the electro-conductive
member in which the occurrence of the C set is suppressed can be
obtained. Further, according to the present invention, the process
cartridge and electrophotographic apparatus capable of stably
forming a high-quality electrophotographic image can be
obtained.
[0014] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1A is a cross-sectional view of a roller-shaped
electro-conductive member according to an embodiment of the present
invention.
[0016] FIG. 1B is a cross-sectional view of the roller-shaped
electro-conductive member according to another embodiment of the
present invention.
[0017] FIG. 2 is a cross-sectional view of an elastic layer in the
present invention.
[0018] FIG. 3A is a schematic view illustrating an embodiment of a
closed cell including a particle according to the present
invention.
[0019] FIG. 3B is a schematic view illustrating an embodiment of a
closed cell including a particle and having a shell according to
the present invention.
[0020] FIG. 4A is a schematic cross-sectional view in an axial
direction illustrating a measurement portion of a thickness of a
conductive resin layer of a conductive roller in the present
invention.
[0021] FIG. 4B is a schematic cross-sectional view in a direction
perpendicular to an axial direction illustrating a measurement
portion of a thickness of the conductive resin layer of the
conductive roller in the present invention.
[0022] FIG. 5 is an explanatory view of a method of measuring an
electrical resistance of the conductive roller.
[0023] FIG. 6 is a schematic view of an electrophotographic
apparatus according to the present invention.
[0024] FIG. 7 is a schematic view of a process cartridge according
to the present invention.
[0025] FIG. 8 is a schematic view of an extruder provided with a
crosshead.
[0026] FIG. 9 is an explanatory view of a die used for producing a
conductive roller according to the present invention.
[0027] FIG. 10 is a schematic view illustrating an abutment state
between a conductive roller and an electrophotographic
photosensitive member.
DESCRIPTION OF THE EMBODIMENTS
[0028] A roller-shaped electro-conductive member (hereinafter
referred to as "conductive roller") according to the present
invention includes an electro-conductive substrate 1 and a porous
rubber elastic layer (hereinafter sometimes simply referred to as
"elastic layer") 2 covering a circumferential surface of the
electro-conductive substrate 1, as FIG. 1A illustrates a
cross-section thereof. Then, as illustrated in FIG. 2, the elastic
layer 2 includes closed cells 51 including particles 52, and the
particles are not fixed to inner walls of the closed cells. That
is, the particles are included in the closed cells so as be movable
independently from the elastic layer. Such particles play a role in
regulating compression deformation of the closed cells. It is to be
noted that, as illustrated in FIG. 1B, the conductive roller
according to the present invention may have a conductive resin
layer 3 on the surface of the elastic layer 2.
[0029] The conductive roller according to the present invention is
used in abutment with an electrophotographic photosensitive member,
for example, and is used as members for various applications of an
electrophotographic apparatus, such as a charging roller, a
developing roller, and a transfer roller.
[0030] Although an example in which a charging roller is used as
the conductive roller is hereinafter described, similar effects can
be expected as long as the conductive roller is an
electrophotographic conductive roller to be used for providing
charge, and the conductive roller is not limited to the charging
roller. As a use example thereof, the charging roller is installed
so as to be brought into abutment with an electrophotographic
photosensitive member and to be connected to a power supply to
apply a bias to a shaft of the charging roller, thereby charging
the electrophotographic photosensitive member to a desired
potential.
[0031] When the charging roller rotates in an image-forming
process, the elastic layer undergoes compression deformation in an
abutment portion with respect to the electrophotographic
photosensitive member. This can ensure an appropriate nip width
between the charging roller and the electrophotographic
photosensitive member, stabilize rotation, and charge the
electrophotographic photosensitive member uniformly. Further, the
elastic layer is brought into abutment with the electrophotographic
photosensitive member even during a period of time excluding the
image-forming process, for example, when left to stand for a long
period of time, and hence the elastic layer undergoes compression
deformation. In the image-forming process, the charging roller
rotates, and hence a particular portion of the elastic layer
undergoes compression deformation for a short period of time. On
the other hand, when left to stand for a long period of time, the
elastic layer is exposed to compression deformation for a long
period of time in its abutment portion with the electrophotographic
member. The elastic layer has viscoelasticity, and hence the
elastic layer shows a larger compression deformation amount when
left to stand than during the image-forming process in which the
charging roller is rotating.
[0032] The charging roller according to the present invention
includes an electro-conductive substrate and an elastic layer.
Then, the elastic layer includes closed cells including particles,
and the particles are not fixed to inner walls of the closed cells.
That is, each of the closed cells has a bell-like structure, and
the particles are included in the closed cells so as to be movable
independently from the elastic layer.
[0033] By configuring the elastic layer as described above, when a
compression deformation amount is small as in the image-forming
process, a compression deformation amount required for ensuring a
nip width can be maintained. On the other hand, in the case where
the elastic layer is compressed by being left to stand over a long
period of time, the particles present in the cells suppress
deformation of the cells due to the compression, and the occurrence
of the C set in the elastic layer can be suppressed.
[0034] Accordingly, it is considered that, by virtue of the
expression of both of an effect of suppressing deformation in the
porous elastic layer when left to stand for a long period of time
and an effect of ensuring a nip width to stabilize rotation, the
occurrence of a set image can be suppressed.
[0035] (Elastic Layer)
[0036] FIG. 2 is a cross-sectional view of the elastic layer 2. The
elastic layer 2 includes the closed cells 51, and each of the
closed cells 51 has a so-called bell-like structure in which the
particles 52 movable independently from the elastic layer 2 are
included in the closed cells 51.
[0037] FIGS. 3A and 3B illustrate enlarged views of the closed cell
51. In FIG. 3A, the particle 52 is included in the closed cell 51
so as not to be fixed to an inner wall of the closed cell, and the
closed cell 51 has a bell-like structure 54 as a whole. Further,
FIG. 3B illustrates a hollow particle structure in which the closed
cell 51 has a shell 53. The particle 52 is included in the hollow
particle structure in a state of not being fixed to the shell
(hereinafter sometimes referred to as "non-fixed state"), and the
closed cell 51 has the bell-like structure as a whole. In any of
these embodiment modes, the effect of the present invention can be
exhibited by virtue of the bell-like structure. A method of
producing the elastic layer is described later in detail.
[0038] When the volume-average particle diameter of the particle 52
is defined as D1 and the volume-average diameter of the closed cell
51 is defined as D2, it is preferred that (D1/D2).sup.3 be 0.1 or
more and 0.8 or less. By setting the volume-average particle
diameters in this range, the particle 52 supports the closed cell
51 when left to stand for a long period of time, and compression
deformation can be suppressed effectively with a repulsion force in
a space within the bell-like structure. Further, it is preferred
that D2 be 20 .mu.m or more and 200 .mu.m or less. By setting D2 in
this range, ensuring of a nip width in the image-forming process,
and suppression of compression deformation in the elastic layer
when left to stand for a long period of time can be achieved
effectively.
[0039] (Rubber Elastic Material)
[0040] Known rubber materials can each be used as a rubber elastic
material to be used in the elastic layer 2. Examples of the rubber
material include natural rubbers, vulcanized natural rubbers, and
synthetic rubbers.
[0041] An ethylene-propylene rubber, a styrene-butadiene rubber
(SBR), a silicone rubber, a urethane rubber, an isoprene rubber
(IR), a butyl rubber, an acrylonitrile-butadiene rubber (NBR), a
chloroprene rubber (CR), an acrylic rubber, an epichlorohydrin
rubber, and a fluororubber can be used as the synthetic
rubbers.
[0042] Those materials may be used alone or as a mixture of two or
more kinds thereof. Further, monomers which are raw materials for
those rubber elastic materials may be copolymerized to be used as a
copolymer.
[0043] (Particle)
[0044] It is preferred that the particle 52 to be included in the
closed cell 51 be a particle having strength capable of suppressing
excess compression and deformation of the closed cell when the
elastic layer is compressed. Examples of the particle capable of
forming such particle are as follows.
[0045] That is, for example, there are given: particles of zinc
oxide, tin oxide, indium oxide, titanium oxides (such as titanium
dioxide and titanium monoxide), iron oxide, strontium titanate,
calcium titanate, magnesium titanate, barium titanate, calcium
zirconate, barium sulfate, molybdenum disulfide, calcium carbonate,
magnesium carbonate, dolomite, talc, kaolin clay, mica, aluminum
hydroxide, magnesium hydroxide, zeolite, wollastonite, diatomaceous
earth, glass beads, bentonite, montmorillonite, an organic metal
compound, and an organic metal salt; iron oxides such as ferrite,
magnetite, and hematite and active carbons; and particles formed of
polymer compounds.
[0046] In this case, specific examples of the polymer compounds may
include: resins such as a polyamide resin, a silicone resin, a
fluororesin, a (meth)acrylic resin, a styrene resin, a phenol
resin, a polyester resin, a melamine resin, a urethane resin, an
olefin resin, an epoxy resin, and copolymers, modified products,
and derivatives thereof; and thermoplastic elastomers such as a
polyolefin-based thermoplastic elastomer, a urethane-based
thermoplastic elastomer, a polystyrene-based thermoplastic
elastomer, a fluororubber-based thermoplastic elastomer, a
polyester-based thermoplastic elastomer, a polyamide-based
thermoplastic elastomer, a polybutadiene-based thermoplastic
elastomer, an ethylene-vinyl acetate-based thermoplastic elastomer,
a polyvinyl chloride-based thermoplastic elastomer, and a
chlorinated polyethylene-based thermoplastic elastomer.
[0047] As long as the particle 52 itself has required strength, the
particle 52 may have a solid structure, a hollow structure, or a
porous structure.
[0048] It is preferred that the content of the particles 52 in the
elastic layer be 2 parts by mass or more and 30 parts by mass or
less with respect to 100 parts by mass of the elastic layer.
[0049] (Preparation of Particle Precursor for Forming Elastic
Layer)
[0050] A method of forming the elastic layer 2 according to the
present invention and a method of preparing a particle precursor
are hereinafter described.
First Embodiment
[0051] A first exemplary embodiment of a method of producing an
elastic layer including closed cells including particles so that
the particles are not fixed to inner walls of the closed cells
according to the present invention is described below.
[0052] First, a particle precursor in which the particle 52 is
impregnated with a volatile substance is prepared. In this case, an
example of the volatile substance is a substance which is a liquid
at normal temperature and which is evaporated by heating during
molding of an elastic layer. Then, a mixture for forming an elastic
layer containing the particle precursor and rubber is prepared.
Then, a layer of the mixture for forming an elastic layer is formed
on the surface of an electro-conductive substrate or the surface of
another layer formed on the surface of the electro-conductive
substrate. Then, the layer of the mixture for forming an elastic
layer is heated to cross-link the rubber in the layer of the
mixture for forming an elastic layer. Due to the heat applied at
this time, an included substance with which the particle precursor
is impregnated is evaporated, and the evaporated included substance
forms a gap at an interface between the particle precursor and the
rubber around the particle precursor, which is being cross-linked.
After that, when the cross-linking of the rubber is completed, a
gap is present between the particle 52 in which the evaporation of
the included substance has been completed and the cross-linked
rubber around the particle 52. As a result, a rubber elastic layer
is formed in which the particle 52 is present in the gap, that is,
a closed cell so that the particle 52 is not fixed to an inner wall
of the closed cell. In this method, the size of a cell can be
adjusted by the kind and amount of the included substance with
which the particle 52 is impregnated.
[0053] Specific examples of the liquid which can be used as the
included substance are as follows.
[0054] For example, there are given water, n-hexane, isohexane,
n-heptane, n-octane, isooctane, n-decane, and isodecane. Further,
as a foaming agent, for example, there are given: organic foaming
agents such as dinitrosopentamethylenetetramine (DPT),
azodicarbonamide (ADCA), p-toluenesulfonyl hydrazine (TSH),
azobisisobutyronitrile (AIBN), and 4,4'-oxybis(benzenesulfonyl
hydrazine) (OBSH); and inorganic foaming agents such as sodium
bicarbonate.
[0055] It is preferred that the particle 52 be a particle having a
porous structure so as to be impregnated with a volatile substance
efficiently.
[0056] An example of the particle having a porous structure is a
porous resin particle.
[0057] The porous resin particle can be produced by any of known
production methods such as a suspension polymerization method, an
interfacial polymerization method, an interfacial precipitation
method, a drying-in-liquid method, and a deposition method
involving adding a solute and a solvent for lowing the solubility
of a resin to a resin solution. For example, in the suspension
polymerization method, a non-polymerizable solvent is dissolved in
a monofunctional polymerizable monomer or a cross-likable monomer
in the presence of a polyfunctional polymerizable monomer, and
aqueous suspension polymerization is performed in an aqueous
solvent containing a surfactant or a dispersion stabilizer. After
the completion of the polymerization, water and the
non-polymerizable solvent can be removed by washing and drying
steps to obtain a porous resin particle. It is to be noted that a
compound having a reactive group which reacts with a functional
group of the polymerizable monomer, an organic filler, or the like
can also be added.
[0058] A (meth)acrylic monomer may be used as the monofunctional
polymerizable monomer. Further, as other monomers, for example,
there may be used: styrene and derivatives thereof, such as
styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene,
p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene,
p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene,
p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene,
n-methoxystyrene, p-phenylsytrene, p-chlorostyrene, and
3,4-dichlorostyrene; ethylene unsaturated monoolefins such as
ethylene, propylene, butylene, and isobutylene, vinyl halides such
as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl
fluoride; and vinyl esters such as vinyl acetate, vinyl propionate,
and vinyl butyrate.
[0059] As the (meth)acrylic monomer, for example, there may be
used: .alpha.-methylene aliphatic monocarboxylates such as methyl
acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate,
propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl
acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl
acrylate, methyl .alpha.-chloroacrylate, methyl methacrylate, ethyl
methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl
methacrylate, n-octyl methacrylate, dodecyl methacrylate,
2-ethylhexyl methacrylate, stearyl methacrylate, phenyl
methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl
methacrylate, diethylaminoethyl acrylate, and diethylaminoethyl
methacrylate; and derivatives of acrylic acid and methacrylic acid,
such as acrylonitrile, methacrylonitrile, acrylamide,
methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,
2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. In
some cases, acrylic acid, methacrylic acid, maleic acid, or fumaric
acid may also be used. However, methyl methacrylate is preferred.
Those monofunctional polymerizable monomers may be used alone or in
combination of two or more kinds thereof.
[0060] Examples of the cross-linkable monomer include ester
(meth)acrylic monomers such as ethylene glycol di(meth)acrylate,
diethylene glycol di(meth)acrylate, triethylene glycol
di(meth)acrylate, decaethylene glycol di(meth)acrylate,
pentadecaethylene glycol di(meth)acrylate, 1,3-butylene glycol
di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol
di(meth)acrylate, glycerin di(meth)acrylate, trimethylolpropane
tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, diethylene
glycol di(meth)acrylate phthalate, hexa(meth)acrylate of
caprolactone modified dipentaerythritol, diacrylate of caprolactone
modified neopentylglycol hydroxypivalate ester, polyester acrylate,
and urethane acrylate; and divinylbenzene, divinylnaphthalene, and
derivatives thereof such as an aromatic divinyl-based monomer.
Those cross-linkable monomers may be used alone or in combination
of two or more kinds thereof.
[0061] The non-polymerizable organic solvent is not particularly
limited, and for example, there may be used toluene, benzene, ethyl
acetate, butyl acetate, n-hexane, n-octane, and n-dodecane. Those
non-polymerizable organic solvents may be used alone or in
combination of two or more kinds thereof.
[0062] The polymerization initiator is not particularly limited,
and is preferably an initiator soluble in the polymerizable
monomer. For example, there may be used a known peroxide initiator
and a known azo initiator. Of those, an azo initiator is preferred,
2,2'-azobisisobutyronitrile, 1,1'-azobiscyclohexane-1-carbonitrile,
2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, and
2,2'-azobis-2,4-dimethylvaleronitrile are more preferred, and
2,2'-azobisisobutyronitrile is particularly preferred. In the case
of the polymerization initiator, the polymerization initiator is
preferably used in an amount of 0.01 part by mass or more and 5
parts by mass or less with respect to 100 parts by mass of the
polymerizable monomer.
[0063] As the surfactant, for example, there may be used: anionic
surfactants such as a sodium lauryl polyoxyethylene ether sulfate
(degree of polymerization: 1 to 100), a sodium lauryl
polyoxyethylene ether sulfate (degree of polymerization: 1 to 100),
and triethanolamine lauryl sulfate; cationic surfactants such as
stearyltrimethylammonium chloride, diethylaminoethylamide lactate
stearate, dilaurylamine hydrochloride, and oleylamine lactate;
nonionic surfactants such as an adipic acid-diethanolamine
condensate, lauryldimethylamine oxide, glycerin monostearate,
sorbitan monolaurate, and diethylaminoethylamide lactate stearate;
and amphoteric surfactants such as cocoamidopropyl betaine,
laurylhydroxysulfobetaine, and sodium (3-laurylaminopropionate.
Further, polymer dispersants such as polyvinyl alcohol, starch, and
carboxymethylcellulose may also be used. In the case of using the
surfactant, it is preferred that the surfactant be used in amount
of 0.01 part by mass or more and 10 parts by mass or less with
respect to 100 parts by mass of the polymerizable monomer.
[0064] Examples of the dispersion stabilizer include organic fine
particles such as polystyrene fine particles, polymethyl
methacrylate fine particles, polyacrylic acid fine particles, and
polyepoxide fine particles, silica such as colloidal silica,
calcium carbonate, calcium phosphate, aluminum hydroxide, barium
carbonate, and magnesium hydroxide. In the case of using the
dispersion stabilizer, it is preferred that the dispersion
stabilizer be used in an amount of 0.01 part by mass or more and 20
parts by mass or less with respect to 100 parts by mass of the
polymerizable monomer.
[0065] It is preferred that the suspension polymerization be
performed in a sealed state through use of a pressure-tight
container. Further, after suspension in a dispersing machine or the
like, suspension polymerization may be performed in a
pressure-tight container, or suspension may be performed in a
pressure-tight container. It is preferred that the polymerization
temperature be 50.degree. C. or more and 120.degree. C. or less.
Although the polymerization may be performed at an atmospheric
pressure, the polymerization is preferably performed under
increased pressure (under increased pressure obtained by adding 0.1
MPa or more and 1 MPa or less to an atmospheric pressure) so that a
non-polymerizable solvent does not become a gas. After the
completion of the polymerization, solid-liquid separation, washing,
and the like may be performed by centrifugation, filtration, and
the like. In the case of performing solid-liquid separation and
washing, drying and crushing may be performed later at a
temperature equal to or lower than the softening temperature of a
resin constituting a porous resin particle. Drying and crushing can
be performed by a known method, and a flash dryer, a fair wind
dryer, a Nauta mixer, or the like can be used. Further, drying and
crushing can also be performed simultaneously with a grinding dryer
or the like. The surfactant and the dispersion stabilizer can be
removed by repeating washing filtration or the like after
production.
[0066] As a method of impregnating the particle 52 with a volatile
substance, in the case where the volatile substance is a liquid,
the particle 52 can be impregnated with the volatile substance by
being placed in the liquid. Further, in the case where the volatile
substance is a solid at normal temperature, for example, a
dispersion in which the volatile substance is dispersed in an
appropriate dispersion medium is prepared, and the particle 52 is
placed in the dispersion to be impregnated with the volatile
substance. In this case, examples of the dispersion medium include
toluene, benzene, ethyl acetate, and butyl acetate. When the inside
of the particle is impregnated with the volatile substance, it is
preferred to perform an ultrasonic treatment. By performing the
ultrasonic treatment, the impregnation amount of an included
substance in the particle 52 can be controlled uniformly. Further,
by adjusting the time of the ultrasonic treatment, the impregnation
amount of the included substance can be adjusted. Thus, a particle
precursor in which the particle 52 is impregnated with the included
substance can be obtained.
Second Embodiment
[0067] A second exemplary embodiment of a method of producing an
elastic layer including closed cells including particles so that
the particles are not fixed to inner walls of the closed cells
according to the present invention is described below.
[0068] First, a particle precursor in which the particle 52 is
coated with a foaming agent is prepared. Then, a mixture for
forming an elastic layer containing the particle precursor and
rubber is prepared. Then, a layer of the mixture for forming an
elastic layer is formed on the surface of an electro-conductive
substrate or the surface of another layer formed on the surface of
the electro-conductive substrate. Then, the layer of the mixture
for forming an elastic layer is heated to cross-link the rubber in
the layer of the mixture for forming an elastic layer. When the
foaming agent with which the particle precursor is coated is foamed
by the heat at this time, a generated gas forms a gap at an
interface between the particle precursor and the rubber around the
particle precursor, which is being cross-linked. After that, when
the cross-linking of the rubber is completed, a gap is present
between the particle 52 and the cross-linked rubber around the
particle 52. As a result, a rubber elastic layer is formed in which
the particle 52 is present in the gap, that is, a closed cell so
that the particle 52 is not fixed to an inner wall of the closed
cell.
[0069] The size of the cell can be adjusted by the kind and amount
of the foaming agent with which the particle 52 is coated. An
example of the foaming agent is a foaming agent used in the
above-mentioned first embodiment.
[0070] An example using a silicone particle as the particle 52 is
hereinafter described. The silicone particle is formed of a
spherical silicone cured substance having a linear
organopolysiloxane block in a molecular structure formula.
[0071] The silicone particle may contain a silicone oil, an
organosilane, an ionorganic powder, an organic powder, and the like
in its particle.
[0072] It is preferred to produce the silicone particle through use
of a composition capable of subjecting a vinyl group-containing
organopolysiloxane (a) and an organohydrogenpolysiloxane (b) to
addition reaction in the presence of a platinum-based catalyst (c),
and curing the reaction product.
[0073] It is necessary that the component (a) have at least two
vinyl groups bonded to a silicon atom in one molecule, and it is
preferred that the vinyl groups be present at least at terminals of
the molecule. Further, the molecular structure may be a linear
structure or a branched structure, or a mixture thereof. Although
there is no particular limit to the molecular weight of the
component (a), it is preferred that the viscosity at a temperature
of 25.degree. C. be 1 cP or more in order that a cured substance
becomes a rubber elastic body.
[0074] The component (b) is a cross-linking agent of the component
(a) and is cured when a hydrogen atom bonded to a silicon atom in
this component undergoes addition reaction with a vinyl group in
the component (a) due to the catalytic function of the component
(c). It is necessary that the component (b) have at least two
hydrogen atoms bonded to a silicon atom in one molecule. There is
no particular limit to the molecular structure of the component
(b), and the molecular structure may be a linear structure, a
branched structure, or a cyclic structure, or a mixture thereof.
Although there is no particular limit to the molecular weight of
the component (b), it is preferred that the viscosity at a
temperature of 25.degree. C. be 1 cP or more and 10,000 cP or less
in order to make the compatibility with the component (a)
satisfactory. Further, regarding the addition amount of this
component, it is preferred that the number of hydrogen atoms bonded
to a silicon atom in this component be 0.5 or more and 20 or less
with respect to one vinyl group in the component (a).
[0075] The component (c) is a catalyst for subjecting a vinyl group
bonded to a silicon atom and a hydrogen atom bonded to a silicon
atom to addition reaction, and examples thereof include
platinum-carrying carbon or silica, chloroplatinic acid, a
platinum-olefin complex, a platinum-alcohol complex, a
platinum-phosphorus complex, and a platinum coordination compound.
It is preferred that the use amount of this component be 1 ppm or
more and 100 ppm in terms of the amount of platinum atoms with
respect to the component (a).
[0076] The silicone particle can be produced by reacting the
component (a) with the component (b) in the presence of the
component (c) and curing the reaction product. Curing can be
performed by, for example, a method of curing the component (a) and
the component (b) in spray drying at high temperature, a method of
curing the components in an organic solvent, or a method of curing
the components after forming the components into an emulsion. Of
those, a method of curing the components in emulsion particles of
silicone is preferred.
[0077] Predetermined amounts of a vinyl group-containing
organopolysiloxane as the component (a) and an
organohydrogenpolysiloxane as the component (b) are mixed to
prepare an organopolysiloxane composition. Then, water and a
surfactant are added to the obtained composition, and the mixture
is emulsified through use of a homomixer or the like. As the
surfactant to be used in this case, non-ionic surfactants such as a
polyoxyethylene alkyl phenyl ether, a polyoxyethylene alkyl ether,
a polyoxyethylene sorbitan fatty acid ester, and a glycerin fatty
acid ester are preferred. It is preferred that the addition amount
of the surfactant fall within the range of 0.01 part by mass or
more and 20 parts by mass of less with respect to 100 parts by mass
of an emulsion.
[0078] It is preferred that the contents of the vinyl
group-containing organopolysiloxane as the component (a) and the
organohydrogenpolysiloxane as the component (b) in the emulsion
fall within the range of 1 part by mass or more and 80 parts by
mass or less. It is to be noted that, in the case where the
silicone rubber spherical fine particles contain a silicone oil, a
silane, an inorganic powder, an organic powder, and the like, these
components only need to be mixed in the organopolysiloxane
composition during emulsification.
[0079] Then, the platinum-based catalyst as the component (c) is
added to the emulsion thus prepared to cure the organopolysiloxane
as a dispersion element of a silicone cured substance. A known
reaction control agent may be added to the platinum-based catalyst,
and in the case where the platinum-based catalyst and the reaction
control agent are hardly dispersed in water, the known reaction
control agent may be added to the platinum-based catalyst after
they are allowed to be dispersed in water through use of a
surfactant. An aqueous dispersion may be subjected to solid-liquid
separation, washing, and the like by centrifugation, filtration,
and the like.
[0080] As a method of coating the particle 52 with a foaming agent,
there is a method involving suspending the particle 52 in a
dispersion of a foaming agent and evaporating the dispersion.
Although the dispersion is not particularly limited, examples
thereof include alcohols such as methanol and ethanol. By adjusting
the foaming agent concentration of the dispersion, the coating
amount of the foaming agent to the particle 52 can be adjusted.
[0081] Thus, a particle precursor in which the particle 52 is
coated with a foaming agent can be obtained.
Third Embodiment
[0082] A third exemplary embodiment of a method of producing an
elastic layer having closed cells including particles so that the
particles are not fixed to inner walls of the closed cells
according to the present invention is described below. In this
embodiment, first, a particle 54 having a so-called bell-like
structure is prepared in which a particle 52 is included in a
hollow particle 51 having a shell 53 so that the particle 52 is not
fixed to a shell inner wall. Then, a mixture for forming an elastic
layer containing the particle 54 and a rubber material is
prepared.
[0083] Next, a layer of the mixture for forming an elastic layer is
formed on the surface of an electro-conductive substrate or the
surface of another layer formed on the surface of the
electro-conductive substrate. Then, the layer of the mixture for
forming an elastic layer is heated to cross-link rubber in the
layer of the mixture for forming an elastic layer. Thus, a rubber
elastic layer is formed in which the particle 52 is present in the
closed cell so that the particle 52 is not fixed to an inner wall
of the closed cell.
[0084] A method of preparing the particle 54 having a bell-like
structure according to this embodiment is hereinafter
described.
[0085] A method of producing the particle having a bell-like
structure is divided into a primary emulsification step, a
secondary emulsification step, a polymerization step, and an
included solvent removal step.
[0086] In the primary emulsification step, to a monomer solution
containing a monomer component and a polymerization initiator, a
nuclear particle dispersion, in which nuclear particles are
dispersed in a polar solution insoluble in the monomer solution, is
added, followed by stirring, to prepare an emulsion in which liquid
droplets made of the nuclear particle dispersion are dispersed in
the monomer solution. The size of a hollow portion of a particle
with a bell-like structure to be obtained corresponds to the size
of the liquid droplet made of the nuclear particle dispersion
obtained in the primary emulsification step.
[0087] In the secondary emulsification step, the emulsion is added
to the polar solution insoluble in a monomer solution and stirred
to prepare an emulsion in which liquid droplets made of a monomer
solution including the nuclear particle dispersion are dispersed in
the polar solution insoluble in a monomer solution. The
emulsification method is not particularly limited, and a
conventionally known method can be used.
[0088] In the polymerization step, the monomer component is
polymerized to obtain a resin particle including the nuclear
particle dispersion. Through the polymerization step, the monomer
component is polymerized and a portion of a shell of a bell-like
particle is formed. The polymerization method is not particularly
limited. An optimum method may be selected appropriately depending
on the kind of a monomer component and a polymerization initiator,
and it is generally preferred to heat the monomer component.
[0089] In the included solvent removal step, the included polar
solution is removed from the resin particle including the nuclear
particle dispersion to obtain a bell-like particle. Although the
method of removing the included solvent is not particularly
limited, vacuum drying or the like is suitable. Through the vacuum
drying, the polar solution included in the bell-like particle
evaporates from a gap of molecules of a shell made of a resin or
from a cell in the case where the monomer solution contains a
non-polymerizable organic solvent.
[0090] Examples of the monomer component include a monofunctional
polymerizable monomer used in the porous resin particle, and a
cross-linkable monomer.
[0091] An example of the polymerization initiator is a
polymerization initiator used in the porous resin particle.
[0092] It is preferred that the monomer solution contain a
lipophilic emulsifier. When the monomer solution contains a
lipophilic emulsifier, emulsification stability of an emulsion to
be obtained in the primary emulsification step can be further
enhanced. The lipophilic emulsifier is not particularly limited,
and examples thereof include a polyoxyethylene alkyl ether, a
polyoxyethylene fatty acid ester, a sorbitan fatty acid ester, a
polyoxyethylene sorbitan fatty acid ester, a glycerin fatty acid
ester, a polyglycerin fatty acid ester, and a propyleneglycol fatty
acid ester. In the case of using the lipophilic emulsifier, it is
preferred that the lipophilic emulsifier be used in an amount of
0.01 part by mass or more and 50 parts by mass or less with respect
to 100 parts by mass of the monomer component.
[0093] The monomer solution may further contain a non-polymerizable
organic solvent. When the monomer solution contains a
non-polymerizable organic solvent, the size of a cell of a shell of
a bell-like particle to be obtained can be adjusted. An example of
the non-polymerizable organic solvent is a non-polymerizable
organic solvent used in the porous resin particle. In the case
where the non-polymerizable organic solvent is blended into the
monomer solution, it is preferred that the non-polymerizable
organic solvent be blended in an amount of 400 parts by mass or
less with respect to 100 parts by mass of the monomer
component.
[0094] The nuclear particle dispersion is a liquid in which nuclear
particles are dispersed in the polar solution insoluble in a
monomer solution. The term "insoluble" as used herein means being
completely separated to form a different phase when mixed, and also
includes the case where solutions are dissolved in each other in a
trace amount. Although there is no particular limit to the polar
solution insoluble in a monomer solution to be used in the primary
emulsification step as long as the polar solution is insoluble in
the monomer solution, water and a polyol such as glycerin are
suitable. It is preferred that the polar solution insoluble in a
monomer solution contain an aqueous polymerization inhibitor. When
the polar solution contains an aqueous polymerization inhibitor,
even in the case where the monomer solution is slightly dissolved
in the polar solution insoluble in a monomer solution,
polymerization can be suppressed. Examples of the aqueous
polymerization inhibitor include sodium nitrite, copper chloride,
iron chloride, titanium chloride, and hydroquinone.
[0095] There is no particular limit to the nuclear particles as
long as they can be dispersed in the polar solution insoluble in a
monomer solution. Examples of the nuclear particles include those
which are illustrated as the particles 52.
[0096] In the primary emulsification step, the nuclear particle
dispersion is added to the monomer solution and emulsified with
stirring. There is no particular limit to the method of
emulsification, and a conventionally known method can be used. As
the polar solution insoluble in a monomer solution to be used in
the secondary emulsification step, those similar to that used in
the primary emulsification step can be used. The polar solution may
be the same as or different from that used in the primary
emulsification step.
[0097] The size of each closed cell 51 in the elastic layer
according to this embodiment can be adjusted by changing the
particle size of the bell-like particle 54.
[0098] (Formation of Elastic Layer)
[0099] The elastic layer can be formed by bonding a sheet- or
tube-shaped layer formed so as to have a predetermined thickness in
advance to the electro-conductive substrate, or by coating the
substrate with the layer. Alternatively, the elastic layer can be
produced by integrally extruding the electro-conductive substrate
and the materials for the elastic layer with an extruder provided
with a crosshead.
[0100] A known method such as mixing with a ribbon blender, a Nauta
mixer, a Henschel mixer, a Super mixer, a Banbury mixer, a pressure
kneader, or the like can be employed as a method of dispersing the
particle precursor in rubber elastic materials to be used for the
elastic layer in the present invention.
[0101] In the case of using the particles precursor according to
the first and second embodiments, it is preferred to heat the
particle precursor so as to form a cell around a particle. At this
time, in order to suppress deformation during foaming, it is
preferred to perform heating with molding with a die or the
like.
[0102] It is preferred that the volume resistivity of the elastic
layer be 1.times.10.sup.2 .OMEGA.cm or more and 1.times.10.sup.10
.OMEGA.cm or less in an environment of a temperature of 23.degree.
C. and a humidity of 50% RH. The volume resistivity of the elastic
layer is determined as follows. First, an elastic layer is cut into
a strip shape measuring about 5 mm by 5 mm by 1 mm. A metal is
deposited on both surfaces of the strip so that an electrode and a
guard electrode may be produced. Thus, a sample for measurement is
obtained. A voltage of 200 V is applied to the resultant sample for
measurement with a microammeter (trade name: ADVANTEST R8340A ULTRA
HIGH RESISTANCE METER, manufactured by Advantest Corporation).
Then, a current after a lapse of 30 seconds is measured, and the
volume resistivity is determined by calculation from the thickness
and an electrode area. The volume resistivity of the elastic layer
can be adjusted with conductive fine particles and an ion
conductive agent. Further, the average particle diameter of the
conductive fine particles is more preferably 0.01 .mu.m or more and
0.9 .mu.m or less, still more preferably 0.01 .mu.m or more and 0.5
.mu.m or less. As long as the average particle diameter falls
within the range, it becomes easy to control the volume resistivity
of the elastic layer.
[0103] In addition, an additive such as a plasticizing oil or a
plasticizer may be added to the elastic layer for adjusting its
hardness or the like. The plasticizer or the like is blended in an
amount of preferably 1 part by mass or more and 30 parts by mass or
less, more preferably 3 parts by mass or more and 20 parts by mass
or less with respect to 100 parts by mass of the rubber elastic
materials. A plasticizer of a polymer type is more preferably used
as the plasticizer. The polymer plasticizer has a weight average
molecular weight of preferably 2,000 or more, more preferably 4,000
or more.
[0104] The hardness of the elastic layer is preferably 70.degree.
or less, more preferably 60.degree. or less in terms of
microhardness (Model MD-1). It is to be noted that the term
"microhardness (Model MD-1)" refers to the hardness of the elastic
layer measured with an ASKER micro-rubber hardness meter (trade
name: MD-1 capa, manufactured by KOBUNSHI KEIKI CO., LTD.).
Specifically, the hardness is a value of the elastic layer, which
has been left to stand in an environment of a temperature of
23.degree. C. and a humidity of 50% RH for 12 hours or more,
measured with the hardness meter according to a 10-N peak hold
mode.
[0105] The elastic layer may be subjected to a surface treatment. A
surface processing treatment with UV or an electron beam, and a
surface modification treatment involving causing a compound or the
like to adhere to the surface and/or impregnating the surface with
the compound or the like can be given as examples of the surface
treatment.
[0106] (Electro-Conductive Substrate)
[0107] An electro-conductive substrate to be used in the
electro-conductive member of the present invention has conductivity
and has a function of supporting a conductive resin layer or the
like to be provided on the electro-conductive substrate. As a
material for the electro-conductive substrate, there may be given
metals such as iron, copper, stainless steel, aluminum, and nickel,
and alloys thereof.
[0108] (Conductive Resin Layer)
[0109] A conductive resin layer may be formed on the elastic layer
of the electro-conductive member of the present invention.
[0110] As a binder to be used in the conductive resin layer, it is
preferred to use a resin from the viewpoints of not contaminating a
photosensitive member and other members and having high
releasability. Any known binder resin may be adopted as a binder
resin. For example, a resin such as a thermosetting resin or a
thermoplastic resin may be used. Of those, a fluororesin, a
polyamide resin, an acrylic resin, a polyurethane resin, an acrylic
urethane resin, a silicone resin, a butyral resin, and the like are
more preferred. Those resins may be used alone or as a mixture of
two or more kinds thereof. Further, copolymers obtained by
copolymerizing monomers which are raw materials for the resins may
be used.
[0111] The electrical resistance of the elastic layer is set as
described above, and hence it is more preferred that the volume
resistivity of the conductive resin layer be 1.times.10.sup.3
.OMEGA.cm or more and 1.times.10.sup.15 .OMEGA.cm or less in an
environment of a temperature of 23.degree. C. and a humidity of 50%
RH.
[0112] The volume resistivity of the conductive resin layer is
determined as follows. First, a conductive resin layer is peeled
from a charging roller and cut into a strip shape measuring about 5
mm by 5 mm. A metal is deposited on both surfaces of the strip so
that an electrode and a guard electrode may be produced. Thus, a
sample for measurement is obtained. Alternatively, a conductive
resin layer coating film is formed on an aluminum sheet by coating,
and a metal is deposited on the coating film surface to obtain a
sample for measurement. The sample for measurement thus obtained
can be measured in the same way as in the method of measuring the
volume resistivity of the elastic layer.
[0113] The volume resistivity of the conductive resin layer can be
adjusted with a conductive agent such as an ion conductive agent or
an electron conductive agent.
[0114] The thickness of the conductive resin layer is preferably
0.1 .mu.m or more and 100 .mu.m or less, more preferably 1 .mu.m or
more and 50 .mu.m or less.
[0115] It is to be noted that the thickness of the conductive resin
layer can be measured by cutting out a section of the roller at a
position illustrated in each of FIGS. 4A and 4B with a keen cutting
tool, and observing the section with an optical microscope or an
electron microscope.
[0116] The conductive resin layer may be subjected to a surface
treatment. A surface processing treatment with UV or an electron
beam, and a surface modification treatment involving causing a
compound or the like to adhere to the surface and/or impregnating
the surface with the compound or the like can be given as examples
of the surface treatment.
[0117] The conductive resin layer can be formed by an application
method such as electrostatic spray application or dipping
application. Alternatively, the conductive resin layer can be
formed by bonding or coating a sheet- or tube-shaped layer formed
so as to have a predetermined thickness in advance. Alternatively,
a method involving curing a material in a mold to mold the material
into a predetermined shape can be employed. Of those, the following
is preferred. A coating is applied by an application method so that
a coating film may be formed.
[0118] When the layer is formed by the application method, a
solvent to be used in the application liquid is not particularly
limited as long as it is a solvent capable of dissolving the
binder. Specific examples thereof include: alcohols such as
methanol, ethanol, and isopropanol; ketones such as acetone, methyl
ethyl ketone, and cyclohexanone; amides such as
N,N-dimethylformamide and N,N-dimethylacetamide; sulfoxides such as
dimethyl sulfoxide; ethers such as tetrahydrofuran, dioxane, and
ethylene glycol monomethyl ether; esters such as methyl acetate and
ethyl acetate; and aromatic compounds such as xylene, ligroin,
chlorobenzene, and dichlorobenzene.
[0119] <Electro-Conductive Member>
[0120] In order to make charging of an electrophotographic
photosensitive member satisfactory, it is more preferred that the
electrical resistance of the electro-conductive member of the
present invention be generally 1.times.10.sup.3.OMEGA. or more and
1.times.10.sup.10.OMEGA. or less in an environment of a temperature
of 23.degree. C. and a humidity of 50% RH.
[0121] With reference to FIG. 5, a method of measuring the
electrical resistance of the charging roller, which is one of the
applications of the electro-conductive member, is described as an
example. Both ends of the electro-conductive substrate 1 are
brought into abutment with a columnar metal 32 having the same
curvature as that of the electrophotographic photosensitive member
by loaded bearings 33a and 33b so as to be parallel to the metal.
In this state, the columnar metal 32 is rotated with a motor (not
shown), and then a DC voltage of -200 V is applied from a
stabilized power supply 34 to a charging roller 5 abutting on the
metal while the roller is rotated following the rotation of the
metal. A current flowing at this time is measured with an ammeter
35, and then the electrical resistance of the charging roller is
calculated.
[0122] The charging roller of the present invention preferably has
such a shape that the charging roller is thickest at a central
portion in its longitudinal direction and becomes thinner as the
charging roller approaches each of both of its ends in the
longitudinal direction, which is so called a crown shape, from the
viewpoint of the uniformization of a longitudinal nip width with
respect to the electrophotographic photosensitive member. A crown
amount is preferably such that a difference between an outer
diameter at the central portion and an outer diameter at a position
90 mm away from the central portion is 30 .mu.m or more and 200
.mu.m or less.
[0123] The hardness of the surface of the charging roller is
preferably 90.degree. or less, more preferably 40.degree. or more
and 80.degree. or less in terms of microhardness (Model MD-1). By
setting the hardness in this range, it becomes easy to stabilize
the abutment between the charging roller and the
electrophotographic photosensitive member or other members.
<Electrophotographic Apparatus>
[0124] FIG. 6 illustrates a schematic configuration of an example
of an electrophotographic apparatus including the conductive roller
of the present invention as a charging roller.
[0125] The electrophotographic apparatus is formed of, for example,
an electrophotographic photosensitive member, a charging device for
charging the electrophotographic photosensitive member, a latent
image-forming device for performing exposure, a developing device,
a transferring device, a cleaning device for recovering transfer
toner on the electrophotographic photosensitive member, and a
fixing device for fixing the toner image.
[0126] An electrophotographic photosensitive member 4 is of a
rotating drum type having a photosensitive layer on an
electro-conductive substrate. The electrophotographic
photosensitive member is rotationally driven in the direction
indicated by an arrow at a predetermined circumferential speed
(process speed).
[0127] The charging device has a contact-type charging roller 5
placed so as to be in contact with the electrophotographic
photosensitive member 4 by being brought into abutment with the
member at a predetermined pressing force. The charging roller 5
rotates following the rotation of the electrophotographic
photosensitive member, and charges the electrophotographic
photosensitive member to a predetermined potential by applying a
predetermined DC voltage from a power supply for charging 19. When
the uniformly charged electrophotographic photosensitive member is
irradiated with exposure light 11 corresponding to image
information, an electrostatic latent image is formed.
[0128] The developing device has a developing sleeve or developing
roller 6 placed so as to be close to, or in contact with, the
electrophotographic photosensitive member 4. The electrostatic
latent image is developed to form a toner image with toner, which
has been subjected to an electrostatic treatment so as to have the
same polarity as the charged polarity of the electrophotographic
photosensitive member, by reversal development. The developing
device includes an elastic regulating blade 13.
[0129] The transferring device has a contact-type transfer roller
8. The device transfers the toner image from the
electrophotographic photosensitive member onto a transfer material
7 such as plain paper (the transfer material is conveyed by a
sheet-feeding system having a conveying member).
[0130] The cleaning device has a blade-type cleaning member 10 and
a recovery container 14, and mechanically scrapes transfer residual
toner remaining on the electrophotographic photosensitive member
after the transfer to recover the toner. In this case, adopting a
simultaneous-with-development cleaning mode according to which the
transfer residual toner is recovered in the developing device can
eliminate the cleaning device.
[0131] A fixing device 9 is formed of a heated roll or the like,
and fixes the transferred toner image onto the transfer material 7
and discharges the resultant to the outside of the apparatus.
<Process Cartridge>
[0132] A process cartridge (FIG. 7) obtained by integrating, for
example, an electrophotographic photosensitive member, a charging
device, a developing device, and a cleaning device, and designed so
as to be attachable to and detachable from an electrophotographic
apparatus can also be used.
[0133] That is, the process cartridge is as described below. A
charging member is integrated with a body to be charged, the
process cartridge is attachable to and detachable from the main
body of the electrophotographic apparatus, and the charging member
is the above-mentioned charging roller.
EXAMPLES
[0134] Now, the present invention is described in more detail by
way of specific examples. However, the present invention is not
limited to these examples.
Production Example 1
Production of Particles 1
[0135] 120 parts by mass of colloidal silica as a dispersion
stabilizer were added to 800 parts by mass of deionized water to
prepare an aqueous mixed solution. Then, an oily mixed solution
made of 60 parts by mass of methyl methacrylate and 40 parts by
mass of ethylene glycol dimethacrylate as polymerizable monomers,
100 parts by mass of ethyl acetate as a non-polymerizable solvent,
and 0.6 part by mass of benzoyl peroxide as a polymerization
initiator was prepared.
[0136] The oily mixed solution was dispersed in the aqueous mixed
solution at a rotation number of 5,000 rpm with a homomixer. After
that, the dispersion thus obtained was loaded in a polymerization
reaction container purged with nitrogen, and suspension
polymerization was performed with stirring at 200 rpm and then
stirring at a temperature of 60.degree. C. for 6 hours to obtain an
aqueous suspension containing resin particles and n-hexane. 0.4
part by mass of sodium lauryl sulfate was added to the aqueous
suspension to adjust the concentration of the sodium lauryl sulfate
to 0.05% by weight with respect to water.
[0137] The obtained aqueous suspension was distilled under reduced
pressure to remove ethyl acetate. The remaining aqueous suspension
was repeatedly subjected to filtration and washing with water,
followed by drying at a temperature of 80.degree. C. for 5 hours,
to produce a particle precursor 1. The volume average particle
diameter of the obtained particle precursor 1 was set to 30 .mu.m
by shredding and classification with an acoustic classifier.
[0138] 10% by weight of the particle precursor 1 were added to
n-hexane that was an included substance. The mixed liquid was
irradiated with an ultrasonic wave for 3 minutes and subjected to
centrifugation at a rotation number of 4,000 rpm for 30 minutes to
remove a supernatant, and thereby, particles 1 impregnated with the
included substance were obtained (see Table 1).
Production Examples 2 to 22
Production of Particles 2 to 22
[0139] Particles 2 to 22 were produced by the same method as that
of Production Example 1 with the exception that the kind and number
of parts of added polymerizable monomers, and an ultrasonic
irradiation time were changed as shown in Table 1.
TABLE-US-00001 TABLE 1 Kind of polymerizable monomer Ultrasonic
Methyl Ethylene glycol Particle irradiation methacrylate
dimethacrylate Styrene Divinylbenzene Colloidal silica diameter
Impregnated time Particle No. (parts by mass) (parts by mass)
(parts by mass) (parts by mass) (parts by mass) (.mu.m) material
(minute(s)) 1 60 40 -- -- 120 30 n-Hexane 3 2 60 40 -- -- 120 30
n-Hexane 6 3 60 40 -- -- 120 45 n-Hexane 1 4 60 40 -- -- 180 15
n-Hexane 10 5 60 40 -- -- 120 48 n-Hexane 1 6 60 40 -- -- 80 60
n-Hexane 6 7 60 40 -- -- 80 80 n-Hexane 3 8 60 40 -- -- 80 65
n-Hexane 3 9 60 40 -- -- 80 90 n-Hexane 1 10 60 40 -- -- 120 30
n-Hexane 10 11 60 40 -- -- 80 94 n-Hexane 1 12 60 40 -- -- 180 15
n-Hexane 10 13 60 40 -- -- 120 25 n-Hexane 3 14 60 40 -- -- 120 27
n-Hexane 1 15 60 40 -- -- 180 10 n-Hexane 10 16 60 40 -- -- 120 27
n-Hexane 1 17 40 30 20 -- 80 60 n-Hexane 3 18 40 30 20 -- 180 15
n-Hexane 10 19 40 30 20 -- 120 48 n-Hexane 1 20 60 -- -- 40 120 30
n-Hexane 3 21 60 -- -- 40 180 20 n-Hexane 10 22 60 -- -- 40 120 50
n-Hexane 1 33 60 40 -- -- 120 30 -- --
Production Example 23
Production of Particles 23
[0140] 500 parts by mass of methylvinylsiloxane represented by the
following formula (1) and having a viscosity of 600 cS and 20 parts
by mass of methylhydrogenpolysiloxane represented by the following
formula (2) and having a viscosity of 30 cS were added to a
polymerization reaction container and mixed with stirring at 2,000
rpm through use of a homomixer.
##STR00001##
[0141] Then, 1 part by mass of polyoxyethylene octyl phenyl ether
and 150 parts by mass of water were added to the mixture, and the
resultant mixture was stirred at 6,000 rpm. As a result, it was
observed that the mixture was thickened. Then, 329 parts by mass of
water were added to the mixture with stirring at 2,000 rpm to
obtain an O/W type emulsion. The emulsion was transferred to a
glass flask equipped with a stirring device having an anchor type
stirring blade, and the temperature was adjusted to 15 to
20.degree. C. After that, a mixture of 1 part by mass of a toluene
solution (platinum content: 0.05%) of a chloroplatinic acid-olefin
complex and 1 part by mass of polyoxyethylene octyl phenyl ether
was added to the resultant emulsion, followed by reaction for 12
hours, to obtain a dispersion. The dispersion was dried to obtain a
particle precursor 23. The volume average particle diameter of the
obtained particle precursor 23 was set to 25 .mu.m by shredding and
classification with an acoustic classifier.
[0142] Next, a methanol solution (containing 10% by mass of ADCA)
of azodicarbonamide (ADCA) that was a foaming agent was prepared.
To the methanol solution, 20% by mass of the particle precursor 23
were added, and the mixture was stirred at 200 rpm. After that,
methanol was removed to obtain particles 23 coated with the foaming
agent (see Table 2).
Production Examples 24 to 27
Production of Particles 24 to 27
[0143] Particles 24 to 27 were produced by the same method as that
of Production Example 23 with the exception that the number of
parts of added methylvinylsiloxane, methylhydrogenpolysiloxane,
polyoxyethylene octyl phenyl ether were changed as shown in Table
2.
TABLE-US-00002 TABLE 2 Number of parts of foaming Kind of reaction
material agent for Polyoxyethylene octyl Particle coating Particle
Methylvinylsiloxane Methylhydrogensiloxane phenyl ether diameter
(part by No. (part by mass) (parts by mass) (parts by mass) (.mu.m)
mass) 23 500 20 1 25 10 24 500 20 0.5 40 20 25 500 20 0.5 45 30 26
500 20 1 15 10 27 800 15 0.5 48 30 34 500 20 1 15 --
Production Example 28
Production of Particles 28
[0144] A mixed solution containing 400 parts by mass of
ion-exchanged water, 8 parts by mass of polyvinyl alcohol
(saponification degree: 85%), and 0.04 part by mass of sodium
lauryl sulfate was prepared. On the other hand, a mixed solution
was prepared in which a mixture containing 0.1 part by mass of
ethylene glycol dimethacrylate, 0.5 part by mass of benzoyl
peroxide, and 100 parts by mass of methyl methacrylate was
dispersed through use of a Viscomill dispersing machine filled with
zirconia beads with a diameter (.phi.) of 0.5 mm. Dispersion was
performed at a circumferential speed of 10 m/sec for 60 hours.
Then, the two kinds of solutions were loaded in a four-necked flask
for two liters equipped with a high-speed stirring device model TK
homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) and
dispersed at a rotation number of 8,000 rpm. After that, the
dispersion was loaded in a polymerization vessel having a stirring
machine and a thermometer, and a space was purged with nitrogen.
Then, the dispersion was continued to be stirred at a temperature
of 60.degree. C. for 12 hours (rotation of the stirring machine: 55
rpm) to complete suspension polymerization. After cooling, the
suspension was filtered, washed, and dried to obtain nuclear
particles 1. The volume average particle diameter of each of the
nuclear particles 1 thus obtained was set to 25 .mu.m by shredding
and classification with an acoustic classifier.
[0145] The nuclear particles 1 were added to ion-exchanged water
containing 1% by weight of sodium chloride and 0.02% by weight of
sodium nitrite as a water-soluble polymerization inhibitor so that
the concentration became 10% by weight. Then, the mixture was
stirred at a rotation number of 5,000 rpm with a homomixer to
obtain a nuclear particle dispersion. Then, 40 parts by weight of
methyl methacrylate and 10 parts by weight of ethylene glycol
dimethacrylate as polymerizable monomers, 0.25 part by weight of
azobisisobutyronitrile (AIBN) as a polymerization initiator, and 2
parts by weight of glycerin monostearate as a lipophilic emulsifier
were prepared. The components were mixed and stirred to prepare a
monomer solution. 50 parts by weight of the nuclear particle
dispersion were added to the monomer solution thus obtained, and
the mixture was stirred and emulsified at a rotation number of
1,000 rpm with a homomixer to obtain a primary dispersion.
[0146] Then, 102.25 parts by weight of the primary dispersion thus
obtained were added to 300 parts by weight of ion-exchanged water
containing 1% by weight of polyvinyl alcohol as a dispersant and
0.02% by weight of sodium nitrite as a water-soluble polymerization
inhibitor. The mixture was stirred and emulsified at a rotation
number of 3,000 rpm with a homomixer to obtain a secondary
dispersion. Then, a polymerization vessel of 20 liters equipped
with a stirring machine, a jacket, a reflux cooler, and a
thermometer was prepared. The polymerization vessel was reduced in
pressure to remove oxygen from the vessel, and a nitrogen
atmosphere was established in the vessel. 10 liters of the obtained
secondary dispersion was loaded in the polymerization vessel at a
time, and the polymerization vessel was raised in temperature to
60.degree. C. to start polymerization with stirring at 200 rpm.
After the polymerization for 4 hours, the polymerization vessel was
further raised in temperature to 80.degree. C., and the content of
the vessel was aged for 1 hour and then cooled to room
temperature.
[0147] The slurry thus obtained was dehydrated with a dehydration
device and dried in vacuum to obtain particles (see Table 3).
Particles having a bell-like structure were obtained. The volume
average particle diameter of each of the obtained particles 28 was
set to 25 .mu.m by shredding and classification with an acoustic
classifier.
Production Examples 29 to 32
Production of Particles 29 to 32
[0148] Particles 29 to 32 were produced by the same method as that
of Production Example 28 with the exception that the stirring
rotation number during production of nuclear particles, the kind
and number of parts of added polymerizable monomers during
production of a primary dispersion, and the stirring rotation
number of the primary dispersion were changed as shown in Table
3.
TABLE-US-00003 TABLE 3 Nuclear particles Primary dispersion
Stirring Polymerizable monomer Stirring rotation Particle Methyl
Ethylene glycol rotation Particle number diameter methacrylate
dimethacrylate number No. Kind (rpm) (.mu.m) (parts by mass) (parts
by mass) (rpm) 28 Methyl 8,000 25 40 10 1,000 methacrylate 29
Methyl 3,000 40 40 10 2,000 methacrylate 30 Methyl 3,000 45 40 10
3,000 methacrylate 31 Methyl 10,000 15 40 10 1,000 methacrylate 32
Methyl 3,000 48 40 10 3,000 methacrylate 35 No nuclear particles 40
10 1,000
Production Example 33
Production of Particles 33
[0149] Particles 33 were produced by the same method as that of
Production Example 1 with the exception that n-hexane was not added
to the particle precursor 1.
Production Example 34
Production of Particles 34
[0150] Particles 34 were produced by the same method as that of
Production Example 26 with the exception that the particle
precursor 26 was not coated with ADCA.
Production Example 35
Production of Particles 35
[0151] Particles 35 were produced by the same method as that of
Production Example 28 with the exception that nuclear particles
were not added.
Production Example 36
Production of Conductive Rubber Composition 1 using Acrylonitrile
Butadiene Rubber
[0152] Materials shown in Table 4 below were kneaded with a
closed-type mixer adjusted to a temperature of 50.degree. C. for 15
minutes.
TABLE-US-00004 TABLE 4 Acrylonitrile butadiene rubber (NBR) 100
parts by mass (trade name: N230SV, manufactured by JSR CORPORATION)
Carbon black 48 parts by mass (trade name: Toka black #7360SB,
manufactured by TOKAI CARBON CO., LTD.) Zinc stearate 1 part by
mass (trade name: SZ-2000, manufactured by SAKAI CHEMICAL INDUSTRY
CO., LTD.) Zinc oxide 5 parts by mass (trade name: Zinc white type
2, manufactured by SAKAI CHEMICAL INDUSTRY CO., LTD.) Calcium
carbonate 20 parts by mass (trade name: Silver W, manufactured by
SHIRAISHI KOGYO CO., LTD.)
[0153] 10 parts by mass of the particles 1, 1.2 parts by mass of
sulfur as a vulcanizing agent, and 4.5 parts by mass of
tetrabenzylthiuram disulfide (TBzTD) (trade name: Perkacit TBzTD
manufactured by Flexis Co., Ltd.) as a vulcanization accelerator
were added to the kneaded materials. The resultant mixture was
kneaded with a two-roll machine cooled to a temperature of
25.degree. C. for 10 minutes to produce a conductive rubber
composition 1.
Production Example 37
Production of Conductive Rubber Composition 2 using Styrene
Butadiene Rubber
[0154] Materials shown in Table 5 below were kneaded with a
closed-type mixer adjusted to a temperature of 80.degree. C. for 15
minutes.
TABLE-US-00005 TABLE 5 Styrene butadiene rubber (SBR) 100 parts by
mass (trade name: SBR1500, manufactured by JSR CORPORATION) Zinc
oxide 5 parts by mass (trade name: Zinc white type 2, manufactured
by SAKAI CHEMICAL INDUSTRY CO., LTD.) Zinc stearate 2 parts by mass
(trade name: SZ-2000, manufactured by SAKAI CHEMICAL INDUSTRY CO.,
LTD.) Carbon black 8 parts by mass (trade name: Ketchen black
EC600JD, manufactured by LION CORPORATION) Carbon black 40 parts by
mass (Trade name: Ceast S, manufactured by TOKAI CARBON CO., LTD.)
Calcium carbonate 15 parts by mass (trade name: silver W,
manufactured by SHIRAISHI KOGYO CO., LTD.) Paraffin oil 20 parts by
mass (trade name: PW380, manufactured by IDEMITSU KOSAN CO.,
LTD.)
[0155] 10 parts by mass of the particles 1, 1 part by mass of
sulfur as a vulcanizing agent, and 1 part by mass of dibenzothiazyl
sulfide (DM) (trade name: NOCCELER DM, manufactured by Ouchi Shinko
Chemical Industrial Co., Ltd.) and 1 part by mass of
tetramethylthiuram monosulfide (TS) (trade name: NOCCELER TS,
manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.) as
vulcanization accelerators were added to the kneaded materials. The
resultant mixture was kneaded with a two-roll machine cooled to a
temperature of 25.degree. C. for 10 minutes to produce a conductive
rubber composition 2.
Production Example 38
Production of Conductive Rubber Composition 3 using Acrylonitrile
Butadiene Rubber
[0156] A conductive rubber composition 3 was produced by the same
method as that of Production Example 36 with the exception that 20
parts by mass of the ADCA were added instead of adding the
particles 1 in Production Example 36.
Production Example 39
Production of Conductive Rubber Composition 4 using Acrylonitrile
Butadiene Rubber
[0157] A conductive rubber composition 4 was produced by the same
method as that of Production Example 36 with the exception that the
particles 1 were changed to the particles 33, and 20 parts by mass
of the ADCA were added in Production Example 36.
Production Example 40
Production of Composite Conductive Fine Particles
[0158] 140 g of methylhydrogenpolysiloxane were added to 7.0 kg of
silica particles (average particle diameter: 15 nm, volume
resistivity: 1.8.times.10.sup.12 .OMEGA.cm), and the resultant was
mixed with stirring at a stirring speed of 22 rpm for 30 minutes
under a linear load of 588 N/cm (60 kg/cm). 7.0 kg of carbon black
"#52" (trade name, manufactured by Mitsubishi Chemical Corporation)
were added to the mixture over 10 minutes while an edge runner was
being operated, and the resultant was mixed with stirring at a
stirring speed of 22 rpm for 60 minutes under a linear load of 588
N/cm (60 kg/cm). Thus, the carbon black was allowed to adhere to
the surfaces of the silica particles coated with
methylhydrogenpolysiloxane, and thereafter, the resultant silica
particles were dried at a temperature of 80.degree. C. for 60
minutes through use of a dryer to produce composite conductive fine
particles. The composite conductive fine particles thus obtained
each had an average particle diameter of 15 nm and a volume
resistivity of 1.1.times.10.sup.2 .OMEGA.cm.
Production Example 41
Production of Surface-Treated Titanium Oxide Particles
[0159] 110 g of isobutyltrimethoxysilane as a surface treatment
agent and 3,000 g of toluene as a solvent were blended into 1,000 g
of needle-like, rutile-type titanium oxide particles (average
particle diameter: 15 nm, vertical:horizontal=3:1, volume
resistivity: 2.3.times.10.sup.10 .OMEGA.cm). Thus, a slurry was
prepared.
[0160] The slurry was mixed with a stirring machine for 30 minutes.
After that, the slurry was supplied to a Viscomill 80% of the
effective internal volume of which had been filled with glass beads
each having an average particle diameter of 0.8 mm, and was then
subjected to a wet shredding treatment at a temperature of
35.+-.5.degree. C. The slurry obtained by the wet shredding
treatment was distilled under reduced pressure with a kneader (bath
temperature: 110.degree. C., product temperature: 30 to 60.degree.
C., degree of decompression: about 100 Torr) so that toluene was
removed. The remainder was subjected to a treatment for baking the
surface treatment agent at a temperature of 120.degree. C. for 2
hours. The particles subjected to the baking treatment were cooled
to room temperature, and were then pulverized with a pin mill.
Thus, surface-treated titanium oxide particles were produced.
Production Example 42
Production of Conductive Resin Coating Liquid 1
[0161] Methyl isobutyl ketone was added to a caprolactone-modified
acrylic polyol solution "PLACCEL DC2016" (trade name, manufactured
by Daicel Chemical Industries, Ltd.) to adjust the solid content of
the mixture to 17% by mass. Components shown in Table 6 below were
added to 588.24 parts by mass of the solution (acrylic polyol solid
content: 100 parts by mass). Thus, a mixed solution was
prepared.
TABLE-US-00006 TABLE 6 Composite conductive fine particles 45 parts
by mass (produced in Production Example 40) Surface-treated
titanium oxide particles 20 parts by mass (produced in Production
Example 41) Modified dimethyl silicone oil "SH28PA" 0.08 part by
mass (trade name, manufactured by DOW CORNING TORAY CO., LTD.)
Block isocyanate mixture 80.14 parts by mass (7:3 mixture of
butanone oxime block bodies of hexamethylene diisocyanate (HDI) and
isophorone diisocyanate (IPDI))
[0162] At this time, the block isocyanate mixture had such an
isocyanate amount that the relationship of "NCO/OH=1.0" is
satisfied.
[0163] Next, 200 g of the mixed solution were loaded into a glass
bottle having an internal volume of 450 mL together with 200 g of
glass beads each having an average particle diameter of 0.8 mm as
media, and then dispersion was performed with a paint shaker
dispersing machine for 24 hours. Then, the glass beads were
removed. Thus, a conductive resin coating liquid 1 was
produced.
Production Example 43
Production of Conductive Resin Coating Liquid 2
[0164] Methyl ethyl ketone was added to a polyurethane resin
"Nippolan 5230" (trade name, manufactured by Nippon Polyurethane
Industry Co., Ltd.) to adjust the solid content of the mixture to
20% by mass. 25 parts by mass of carbon black "MA230" (trade name,
manufactured by Mitsubishi Chemical Corporation) as a conductive
agent were added to 214.29 parts by mass of the solution
(polyurethane resin solid content: 100 parts by mass), and the
resultant was treated with a ball mill for 5 hours to obtain a
resin coating material 2 in which carbon black was dispersed. 40
parts by mass of an alkyl isocyanate-modified polyethyleneimine
were added to the resin coating material 2.
[0165] Then, 15 parts by mass of urethane particles "Art Pearl
C-400T" (trade name, manufactured by Negami Chemical Industrial
Co., Ltd.) were added to the mixture, and the resultant mixture was
thoroughly stirred. After that, methyl ethyl ketone was added to
the mixture to adjust the viscosity to 7 mPas to obtain a
conductive resin coating liquid 2. The viscosity was measured at a
cone rotor rotation number of 20 rpm and at a liquid temperature
adjusted to 25.degree. C., through use of an E-type viscometer
(RE115L (trade name), manufactured by Toki Sangyo Co., Ltd.) and a
standard cone rotor with a cone angle of 1.degree. 34'.
Example 1
Charging Roller 1
[0166] (Electro-Conductive Substrate)
[0167] A stainless-steel substrate having a diameter of 6 mm and a
length of 252.5 mm was coated with a thermosetting adhesive
containing 10% by mass of carbon black and dried to be used as an
electro-conductive substrate.
[0168] (Formation of Elastic Layer)
[0169] An electro-conductive substrate was coated with the
conductive rubber composition 1 produced in Production Example 36
in a cylindrical shape coaxially with the electro-conductive
substrate being a center axis, through use of an extruder provided
with a crosshead illustrated in FIG. 8 to produce a preform. The
thickness of the rubber composition used for the coating was
adjusted to 1.75 mm. It is to be noted that, in FIG. 8, an
electro-conductive substrate is represented by 1, a feed roller is
represented by 42, an extruder is represented by 40, a crosshead is
represented by 41, and a roller after extrusion is represented by
43.
[0170] The rubber composition at the ends of the preform was
removed to expose the ends of the electro-conductive substrate.
Then, as FIG. 9 schematically illustrates the preform, the preform
was set in a die 45 having a cylindrical cavity 44 with an inner
diameter (.phi.) of 12 mm, and the preform was heated and foamed.
The die was heated at a temperature of 160.degree. C. for 20
minutes through use of a heater and a temperature-adjusting device
(not shown). Further, the resultant was taken out from the die, and
then subjected to secondary vulcanization by heating at a
temperature of 160.degree. C. for 30 minutes with a hot-air oven to
obtain an elastic roller 1 having an elastic layer with an outer
diameter (.phi.) of 12 mm and a length of 224.2 mm.
[0171] (Production of Charging Roller 1)
[0172] The conductive resin coating liquid 1 produced in Production
Example 42 was applied onto the elastic roller 1 thus produced once
by dipping, and was then air-dried at normal temperature for 30
minutes. After that, the resultant was dried with a circulating hot
air dryer at a temperature of 80.degree. C. for 1 hour and then at
a temperature of 160.degree. C. for an additional one hour. Thus, a
charging roller 1 was obtained.
[0173] In this case, the dipping application was performed under
the conditions of an immersion time of 9 seconds, an initial
dip-coating lifting speed of 20 mm/sec, and a final dip-coating
lifting speed of 2 mm/sec. The lifting speed was linearly changed
with time in the course of the dipping application.
[0174] (Measurement of Electrical Resistance of Charging
Roller)
[0175] The resistance of the charging roller was measured with an
instrument for measuring an electrical resistance illustrated in
FIG. 5.
[0176] First, the charging roller was brought into abutment with a
columnar metal 32 (having a diameter of 30 mm) by bearings 33a and
33b so that the charging roller was parallel to the metal.
[0177] In this case, an abutment pressure was adjusted to 4.9 N at
one end, i.e., a total of 9.8 N at both ends with a spring
pressure.
[0178] Next, the charging roller was rotated with a motor (not
shown) following the columnar metal 32 rotationally driven at a
circumferential speed of 45 mm/sec.
[0179] During the rotation following the metal, a DC voltage of
-200 V was applied from a stabilized power supply 34, and then a
value for a current flowing through the charging roller was
measured with an ammeter 35. The resistance of the charging roller
was calculated from the applied voltage and the current value.
[0180] The charging roller was left to stand still in an
environment of a temperature of 23.degree. C. and a humidity of 50%
RH for 24 hours or more before its electrical resistance was
measured. As a result, the electrical resistance of the charging
roller 1 was 2.0.times.10.sup.5.OMEGA..
[0181] (Shape Measurement of Elastic Layer Cross-Section)
[0182] An arbitrary point of the elastic layer was cut every 20 nm
over 500 .mu.m with focused ion beams (trade name: FB-2000C,
manufactured by Hitachi, Ltd.), and then its cross-sectional images
were photographed. Then, images obtained by photographing cells and
particles were combined to calculate a stereoscopic image.
[0183] A particle diameter dl and a closed cell diameter d2 were
measured from the stereoscopic image to calculate the volume
average particle diameter D1 of the particle and the volume average
diameter D2 of the closed cell illustrated in FIGS. 3A and 3B. That
is, the particle diameter dl and the closed cell diameter d2 were
measured for ten particles and cells in a viewing field,
respectively. Then, the same measurement was performed with respect
to 10 points in a longitudinal direction of the elastic layer, and
average values of a total of 100 particles and cells were
respectively calculated to obtain the volume average particle
diameter D1 and the volume average diameter D2 of the closed
cell.
[0184] Further, it was confirmed by the following method that the
particles in the closed cells of the elastic layer were not fixed
to inner walls of the closed cells.
[0185] That is, a center portion in the longitudinal direction of
the elastic layer was cut with the focused ion beams (trade name:
FB-2000C, manufactured by Hitachi, Ltd.), and a cross-section
thereof was observed with a manipulator (trade name: AxisPro Micro
Manipulator, manufactured by Micro Support Co., Ltd.).
[0186] Then, the particles present in the closed cells in the
viewing field were collected through use of a microtool (metallic
probe) of the manipulator. Thus, it was confirmed that the
particles were not fixed to the inner walls of the closed cells.
This operation was performed for closed cells at 10 places in the
viewing field. Further, the same operation was also performed for
two places at positions of 90 mm away from the center portion in
the longitudinal direction of the elastic layer to both ends,
respectively. That is, 30 closed cells present in the elastic layer
were observed, and it was confirmed that the particles present in
the respective closed cells had a bell-like structure in which the
particles were not fixed to the inner walls of the closed cells and
were movable in the closed cells independently from an elastic
body.
[0187] (Evaluation of Horizontal Line Image Due to Set)
[0188] As an electrophotographic apparatus having a configuration
illustrated in FIG. 6, a color laser jet printer (trade name: HP
Color LaserJet 4700dn) manufactured by Hewlett-Packard Co. Ltd. was
remodeled so as to have an output speed of a recording medium of
200 mm/sec (A4 vertical output) to be used. The image resolution
was 600 dpi, and the output of primary charging was a DC voltage of
-1,100 V.
[0189] As a process cartridge having a configuration illustrated in
FIG. 7, a process cartridge (for black) for the printer was
used.
[0190] An accompanying charging roller was taken out from the
above-mentioned process cartridge, and the charging roller
according to the present invention was set. The charging roller was
brought into abutment with the photosensitive member under a spring
pressure of 4.9 N at one end (total 9.8 N at both terminals) (FIG.
10).
[0191] The process cartridge was left to stand still for 1 month in
an environment of a temperature of 40.degree. C. and a humidity of
95% RH (left to stand under harsh conditions). After that, the
process cartridge was left to stand still for 6 hours in an
environment of a temperature of 23.degree. C. and a humidity of 50%
RH, and then mounted on the above-mentioned electrophotographic
apparatus, and an image was output in the same environment. As an
evaluation image, a half-tone image (image drawing horizontal lines
at a width of one dot in a direction perpendicular to the rotation
direction of the photosensitive member at an interval of two dots)
was output. The output image was evaluated for its set image based
on the criteria described in the Table 7 below. Table 8 shows the
evaluation results.
TABLE-US-00007 TABLE 7 Rank 1 No set image is generated. Rank 2
Only a slight stripe-like image is recognized. Rank 3 Although a
stripe-like image is partly recognized at a pitch of the charging
roller, image quality has no practical problem. Rank 4 A
stripe-like image is conspicuous, and degradation in image quality
is recognized.
[0192] (Measurement of Set Amount)
[0193] After outputting an image, the charging roller was taken out
from the process cartridge, and radii of the charging roller in a
set portion and a non-set portion were respectively measured. For
the measurement, an automatic roller measurement apparatus
manufactured by Tokyo Opto-Electronics Co., Ltd. was used.
[0194] Regarding three positions: a center position in a
longitudinal direction of the charging roller, and positions 90 mm
away from the center position to the left and right, the charging
roller was rotated by 1.degree. each time, and the positions
corresponding to the set portion and the non-set portion were
measured. Next, a difference between a maximum value of the radius
of the non-set portion and a minimum value of the radius of the set
portion was calculated. A value at which the difference in radius
was largest of the three portions was defined as a set amount in
the present invention. Table 8 shows the results.
[0195] With the charging roller according to this example, a set
image was not generated, and a satisfactory image was obtained.
Examples 2 to 18
Charging Rollers 2 to 18
[0196] Charging rollers 2 to 18 were produced in the same way as in
Example 1 with the exception that the kind and number of parts of
added particles were changed as shown in Table 8. Table 8 shows the
results.
Example 19
Charging Roller 19
[0197] A charging roller 19 was produced in the same way as in
Example 1 with the exception that the conductive rubber composition
1 was changed to the conductive rubber composition 2 produced in
Production Example 37. Table 8 shows the results.
Examples 20 to 22
Charging Rollers 20 to 22
[0198] Charging rollers 20 to 22 were produced in the same way as
in Example 19 with the exception that the kind and number of parts
of added particles were changed as shown in Table 8. Table 8 shows
the results.
Example 23
Charging Roller 23
[0199] A charging roller 23 was produced in the same way as in
Example 1 with the exception that the kind and number of parts of
added particles were changed as shown in Table 8. Table 8 shows the
results.
Examples 24 to 26
Charging Rollers 24 to 26
[0200] Charging rollers 24 to 26 were produced in the same way as
in Example 19 with the exception that the kind and number of parts
of added particles were changed as shown in Table 8. Table 8 shows
the results.
Example 27
Charging Roller 27
[0201] A charging roller 27 was produced in the same way as in
Example 19 with the exception that the conductive resin coating
liquid was not applied in Example 19. Table 8 shows the
results.
Examples 28 to 32
Charging Rollers 28 to 32
[0202] Charging rollers 28 to 32 were produced in the same way as
in Example 1 with the exception that the kind and number of parts
of added particles were changed as shown in Table 8. Table 8 shows
the results.
Example 33
Charging Roller 33
[0203] A charging roller 33 was produced in the same way as in
Example 19 with the exception that the kind and number of parts of
added particles were changed as shown in Table 8. Table 8 shows the
results.
Example 34
Electro-Conductive Substrate
[0204] A stainless-steel substrate having a diameter of 6 mm and a
length of 252.5 mm was coated with a thermosetting adhesive
containing 10% by mass of carbon black and dried to be used as an
electro-conductive substrate.
[0205] (Formation of Elastic Layer)
[0206] An electro-conductive substrate was coated with the same
conductive rubber composition as the conductive rubber composition
1 produced in Production Example 36 with the exception that the
particles were changed to the particles 28 and the number of parts
of added particles was changed to 15 parts by mass in a cylindrical
shape coaxially with the electro-conductive substrate being a
center axis, through use of an extruder provided with a crosshead
illustrated in FIG. 8 to produce a preform. The thickness of the
rubber composition used for the coating was adjusted to 3 mm.
[0207] An elastic roller 34 having an elastic layer with an outer
diameter (.phi.) of 12 mm and a length of 224.2 mm was obtained by
the same method as that of the elastic roller 1 in Example 1.
[0208] (Production of Charging Roller 34)
[0209] The conductive resin coating liquid 1 produced in Production
Example 42 was applied onto the elastic roller 34 thus produced
once by dipping by the same method as that of the charging roller 1
in Example 1 to obtain a charging roller 34. The obtained charging
roller 34 was measured for its electrical resistance and shape and
evaluated for its image in the same way as in Example 1. Table 8
shows the results.
Examples 35 to 38
[0210] Charging rollers 35 to 38 were produced by the same method
as in Example 34 with the exception that the kind and number of
parts of added particles were changed as shown in Table 8. Table 8
shows the results.
Example 39
[0211] A charging roller 39 was produced by the same method as in
Example 34 with the exception that the conductive rubber
composition 1 was changed to the conductive rubber composition 2
produced in Production Example 37, and the kind and number of parts
of added particles were changed as shown in Table 8. Table 8 shows
the results.
Comparative Example 1
[0212] A charging roller 40 was produced by the same method as that
of Example 1 with the exception that the conductive rubber
composition 1 was changed to the conductive rubber composition 3
produced in Production Example 38, and the kind and number of parts
of added particles were changed as shown in Table 8 in Example 1.
Table 8 shows the results.
Comparative Example 2
[0213] A charging roller 41 was produced by the same method as that
of Example 1 with the exception that the conductive rubber
composition 1 was changed to the conductive rubber composition 4
produced in Production Example 39, and the kind and number of parts
of added particles were changed as shown in Table 9 in Example 1.
Table 8 shows the results.
Comparative Example 3
[0214] A charging roller 42 was produced by the same method as that
of Comparative Example 2 with the exception that the particles 33
were changed to the particles 34, and the kind and number of parts
of added particles were changed as shown in Table 8 in Comparative
Example 2. Table 8 shows the results.
Comparative Example 4
[0215] A charging roller 43 was produced by the same method as that
of Comparative Example 2 with the exception that the particles 33
were changed to the particles 35, and the ADCA was not added in
Comparative Example 2. Table 8 shows the results.
TABLE-US-00008 TABLE 8 Amount of Roller Particle Cell Charging
Particle added particles resistance diameter D1 diameter D2 Set
amount roller No. No. (parts by mass) (.OMEGA.) (.mu.m) (.mu.m)
(D1/D2).sup.3 Set image (.mu.m) Example 1 1 1 10 2.0 .times.
10.sup.5 30 40 0.42 1 9 2 2 1 15 1.6 .times. 10.sup.6 30 43 0.34 1
10 3 3 1 20 1.2 .times. 10.sup.5 30 46 0.28 1 9 4 4 2 15 1.1
.times. 10.sup.5 30 50 0.22 2 11 5 5 3 12 2.6 .times. 10.sup.5 45
50 0.73 1 10 6 6 4 15 1.2 .times. 10.sup.5 15 50 0.03 3 13 7 7 5 15
1.2 .times. 10.sup.5 48 50 0.88 3 13 8 8 6 15 2.8 .times. 10.sup.5
60 95 0.25 2 12 9 9 7 15 1.1 .times. 10.sup.5 80 110 0.38 1 9 10 10
8 15 2.7 .times. 10.sup.5 65 90 0.38 1 9 11 11 9 15 1.4 .times.
10.sup.5 90 102 0.69 1 10 12 12 10 15 1.3 .times. 10.sup.5 30 70
0.08 3 13 13 13 11 15 9.7 .times. 10.sup.4 94 99 0.86 3 12 14 14 12
20 1.2 .times. 10.sup.5 15 26 0.19 2 11 15 15 13 20 1.2 .times.
10.sup.6 25 30 0.58 1 10 16 16 14 20 1.6 .times. 10.sup.5 27 30
0.73 1 10 17 17 15 20 2.8 .times. 10.sup.5 10 25 0.06 3 12 18 18 16
20 1.7 .times. 10.sup.5 27 28 0.90 3 13 19 19 1 10 5.3 .times.
10.sup.5 30 42 0.36 1 9 20 20 17 15 2.1 .times. 10.sup.5 60 70 0.63
1 9 21 21 18 15 1.1 .times. 10.sup.5 15 45 0.04 3 13 22 22 19 15
2.9 .times. 10.sup.5 48 51 0.83 3 12 23 23 17 15 7.6 .times.
10.sup.5 60 69 0.66 1 9 24 24 20 15 2.4 .times. 10.sup.5 30 44 0.32
1 9 25 25 21 15 2.3 .times. 10.sup.5 20 44 0.09 3 12 26 26 22 15
9.9 .times. 10.sup.4 50 52 0.89 3 13 27 27 1 10 1.8 .times.
10.sup.6 30 40 0.42 1 10 28 28 23 15 3.5 .times. 10.sup.5 25 46
0.16 2 10 29 29 24 15 1.2 .times. 10.sup.5 40 53 0.43 1 9 30 30 25
15 1.1 .times. 10.sup.5 45 51 0.69 1 10 31 31 26 15 3.7 .times.
10.sup.5 15 51 0.03 3 13 32 32 27 15 2.6 .times. 10.sup.5 48 51
0.83 3 13 33 33 24 15 4.5 .times. 10.sup.5 40 52 0.46 1 9 34 34 28
15 3.7 .times. 10.sup.5 25 52 0.11 2 11 35 35 29 15 1.7 .times.
10.sup.6 40 50 0.51 1 10 36 36 30 15 1.7 .times. 10.sup.6 45 49
0.77 1 9 37 37 31 15 1.8 .times. 10.sup.6 15 50 0.03 3 12 38 38 32
15 7.6 .times. 10.sup.5 48 50 0.88 3 13 39 39 29 15 1.7 .times.
10.sup.6 40 51 0.48 1 10 Comparative 1 40 -- -- 2.2 .times.
10.sup.6 -- 53 -- 4 16 example 2 41 33 15 2.6 .times. 10.sup.6 --
48 -- 4 15 3 42 34 15 9.3 .times. 10.sup.5 -- 46 -- 4 15 4 43 35 15
1.2 .times. 10.sup.5 -- 51 -- 4 16
[0216] (Production and Evaluation of Developing Roller)
Example 40
Electro-Conductive Substrate
[0217] A stainless-steel substrate having a diameter of 6 mm and a
length of 240 mm was coated with a thermosetting adhesive
containing 10% by mass of carbon black and dried to be used as an
electro-conductive substrate.
[0218] (Formation of Elastic Layer)
[0219] An electro-conductive substrate was coated with the
conductive rubber composition 1 produced in Production Example 36
in a cylindrical shape coaxially with the electro-conductive
substrate being a center axis, through use of an extruder provided
with a crosshead illustrated in FIG. 8 to produce a preform. The
thickness of the coated rubber composition was adjusted to 1.75 mm.
An elastic roller 40 having an elastic layer with an outer diameter
(.phi.) of 12 mm and a length of 232 mm was obtained by the same
method as that of the elastic roller 1 in Example 1.
[0220] (Production of Developing Roller 1)
[0221] The conductive resin coating liquid 2 produced in Production
Example 43 was once applied onto the elastic roller 40 thus
produced by dipping by the same method as that of the charging
roller 1 in Example 1 to obtain a developing roller 1.
[0222] (Measurement of Electrical Resistance of Developing
Roller)
[0223] The resistance of the developing roller was measured with an
instrument for measuring an electrical resistance illustrated in
FIG. 5.
[0224] First, the developing roller was brought into abutment with
a columnar metal 32 (having a diameter of 50 mm) by bearings 33a
and 33b so that the developing roller was parallel to the
metal.
[0225] In this case, the abutment pressure was adjusted to 4.9 N at
one end, i.e., a total of 9.8 N at both ends with a spring
pressure.
[0226] Next, the developing roller was rotated with a motor (not
shown) following the columnar metal 32 rotationally driven at a
circumferential speed of 50 mm/sec.
[0227] During the rotation following the metal, a DC voltage of +50
V was applied from a stabilized power supply 34, and then a value
for a current flowing through the developing roller was measured
with an ammeter 35. The resistance of the developing roller 1 was
calculated from the applied voltage and the current value. The
developing roller 1 was left to stand still in an environment of a
temperature of 23.degree. C. and a humidity of 50% RH for 24 hours
or more before its electrical resistance was measured. As a result,
the electrical resistance of the developing roller 1 was
1.0.times.10.sup.5.OMEGA..
[0228] (Shape Measurement of Elastic Layer Cross-Section)
[0229] The shape measurement of the elastic layer was performed by
the same method as that of Example 1.
[0230] (Evaluation of Horizontal Line Image Due to Set)
[0231] As an electrophotographic apparatus having a configuration
illustrated in FIG. 6, a color laser printer LBP5400 (trade name)
manufactured by Canon Inc. was remodeled so as to have an output
speed of a recording medium of 200 mm/sec (A4 vertical output) to
be used. The image resolution was 600 dpi, and the output of
primary charging was a DC voltage of -1,100 V.
[0232] As a process cartridge having a configuration illustrated in
FIG. 7, a process cartridge (for black) for the printer was
used.
[0233] An accompanying charging roller was taken out from the
above-mentioned process cartridge, and the charging roller
according to the present invention was set in an abutment
state.
[0234] The process cartridge was left to stand still for 1 month in
an environment of a temperature of 40.degree. C. and a humidity of
95% RH (left to stand under harsh conditions). Then, the process
cartridge was left to stand still for 6 hours in an environment of
a temperature of 23.degree. C. and a humidity of 50% RH, and then
mounted on the above-mentioned electrophotographic apparatus, and
an image was output in the same environment. As an evaluation
image, a half-tone image (image drawing horizontal lines at a width
of one dot in a direction perpendicular to the rotation direction
of the photosensitive member at an interval of two dots) was
output. The output image was evaluated for its set image based on
the criteria described in the Table 9 below. Table 10 shows the
evaluation results.
TABLE-US-00009 TABLE 9 Rank 1 No set image is generated. Rank 2
Only a slight stripe-like image is recognized. Rank 3 Although a
stripe-like image is partly recognized at a pitch of the charging
roller, image quality has no practical problem. Rank 4 A
stripe-like image is conspicuous, and degradation in image quality
is recognized.
[0235] (Measurement of Set Amount)
[0236] A set amount was measured by the same method as that of
Example 1.
[0237] With the developing roller 1 according to this example, a
set image was not generated, and a satisfactory image was
obtained.
Examples 41 to 44
[0238] Developing rollers 2 to 5 were produced by the same method
as that of Example 40 with the exception that the kind and number
of parts of added particles were changed as shown in Table 10.
Table 10 shows the results.
Comparative Example 5
[0239] A developing roller 6 was produced by the same method as
that of Example 1 with the exception that the conductive rubber
composition 1 was changed to the conductive rubber composition 3
produced in Production Example 38, and the kind and number of parts
of added particles were changed as shown in Table 10 in Example 40.
Table 10 shows the results.
Comparative Example 6
[0240] A developing roller 7 was produced by the same method as
that of Example 1 with the exception that the conductive rubber
composition 1 was changed to the conductive rubber composition 4
produced in Production Example 39, and the kind and number of parts
of added particles were changed as shown in Table 10 in Example 40.
Table 10 shows the results.
TABLE-US-00010 TABLE 10 Amount of added particles Roller Particle
Cell diameter Evaluation Set Developing (parts by resistance
diameter D1 D2 of Set amount roller No. Particle No. mass)
(.OMEGA.) (.mu.m) (.mu.m) (D1/D2).sup.3 image (.mu.m) Example 40 1
1 10 1.0 .times. 10.sup.5 30 41 0.39 1 10 41 2 2 15 2.1 .times.
10.sup.5 30 48 0.24 2 11 42 3 3 12 1.6 .times. 10.sup.5 45 51 0.69
1 10 43 4 4 15 5.2 .times. 10.sup.5 15 50 0.03 3 13 44 5 5 15 4.7
.times. 10.sup.5 48 51 0.83 3 13 Comparative 5 6 -- -- 3.8 .times.
10.sup.6 -- 51 -- 4 16 Example 6 7 33 15 2.3 .times. 10.sup.6 -- 46
-- 4 15
[0241] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0242] This application claims priority from Japanese Patent
Application No. 2011-267222 filed on Dec. 6, 2011, the content of
which is hereby incorporated by reference.
* * * * *